Telescopic antenna



April 23, 1968 GEORGE 3,380,062

TELESCOPIC ANTENNA Filed April 26, 1967 INVENTOR. MICHAEL P. GEORGE W QZZ VOJZ 1 ATTOR N EYS United States Patent 3,380,062 TELESCOPIC ANTENNA Michael P. George, deceased, late of Lexington, Mass, by Jeanette S. George, executrix, 55 Jacqueline Road, Waltham, Mass. Continuation-impart of application Ser. No. 378,176, June 26, 1964. This application Apr. 26, 1967, Ser. No. 642,992

Claims. (Cl. 343-903) ABSTRACT OF THE DESCLOSURE A telescopic radio antenna is provided with conductive coil spring elements connecting adjacent telescopic sections, forming part of the antenna circuit and maintaining electrical contact between antenna sections regardless of telescopic extent or antenna position.

Cross-reference to related application This application is a continuation-in-part of US. ap plication Ser. No. 378,176 filed June 26, 1964, and now abandoned.

This invention relates generally to radio antennas and more particularly is directed towards a new and improved telescopic radio antenna of the sort employed in mobile units such as automobiles and the like.

In conventional telescopic antennas individual sections are mechanically but not electrically connected together. As a result, the antenna circuit is subject to interruption if good electrical contact between the parts is not maintained. The problem is especially critical with transmitting antennas where an uninterrupted antenna circuit is essential for proper operation. Heretofore, telescopic transmitting antennas have not been used to any great extent because of poor or inefiicient electrical connections between the antenna sections. This is particularly critical in automobile antennas which often whip back and forth, because of changes in speed, and this tends to produce circuit interruptions between adjacent telescopic sections. As a result, one piece antennas are most frequently used. These one piece units, while eflicient for transmitting purposes must normally be made quite long as determined by the transmitting frequency. The one piece antennas, unless bent over in some fashion, strike trees, bridges and other overhanging objects when the automobile is moving.

Accordingly, it is an object of the present invention to provide improvements in telescopic antennas.

Another object of this invention is to provide a telescopic antenna in which the antenna sections are both mechanically and electrically connected throughout their entire range of extension.

Yet another object of this invention is to provide a novel means for mounting a telescopic antenna.

More particularly, this invention features a telescopic antenna comprising a plurality of antenna sect-ions telescopically connected to one another with coil spring elements electrically connecting each adjacent element to provide a continuous electrical circuit from one end of the antenna to the other through any telescoped extent of the several sections or through any antenna position. The invention also features a novel swivel mount for the antenna which will accommodate power mechanism for automatically raising or lowering the antenna. In association with the antenna power drive system is a novel arrangement for guiding a drive element through a helical spring mount without interruption of the electrical circuit. The antenna may be extended or retracted while the car is in motion and lowered for garaging purposes.

This invention also features a novel arrangement for ice maintaining the antenna sections in a tionship with respect to one another.

However, these and other features of the invention, along with further objects and advantages thereof, will become more fully apparent from the following detailed description of a preferred embodiment of the invention, with reference being made to the accompanying drawings, in which:

FIG. 1 is a sectional view in side elevation showing a telescopic antenna made according to the invention,

FIG. 2 is a detailed sectional view in side elevation showing a section of the antenna of FIG. 1 in a retracted condition,

FIG. 3 is a cross-sectional view taken along the line 3-3 of FIG. 1, and

FIG. 4 is a detailed sectional view in side elevation showing a modification of the invention.

Referring now to the drawings, the reference character 10 generally indicates a telescopic antenna mounted to a selected portion, such as a fender or the like, of an automobile body 12. The antenna comprises a plurality of telescoped sections 14, 16 and 18 connected by a heavy coil spring 20 to a swivel ball mount 22 connected to the car body 12. Mounted within the car body is a motor 24 providing the necessary drive for power extension or retraction of the antenna. Connection between the antenna and the transmitter is made by means of a lead 26 connected to a tapped annular adapter 28 located above the mot-or 24.

The mounting for the motor 24 includes an annular adapter 30 adapted to slip down over a cylindrical head 32 mounted on the motor 24 and accommodating a flexible nylon rod 34 which is adapted to extend up through the center of the antenna. The motor is drivingly connected to a drum 36 about which the lower portion of the rod 34 is wound. The nylon rod has its upper end connected to the topmost portion of the antenna and it will be understood that the motor 24, which is reversible, can feed out or retract the rod so as to extend or retract the telescoped antenna sections. Electrically insulating the motor from the antenna is a shouldered annular coupling 40 of electrically insulating material connecting the adapters 28 and 30.

Screwed into the uppermost adapter 28 is a threaded stem 42 of the split ball mount 22. This stem extends down from the lowermost portion of the ball mount and passes through an opening formed in the automobile body 12. The mount is clamped in position by means of a flange 46 .at the base of the ball mount and at the outer surface of the body panel 12 and by means of a nut 48 on the innerside of the panel 12 and threaded over the stem 42. An insulating washer 50 is mounted between the nut 48 and the body panel 12 and a rubber washer 52 is mounted between the flange 46 and the body panel.

It will be noted that the assembly defines a central passage 54 through which extends the flexible nylon rod 34. This passage also extends vertically through the ball mount 22 which will be seen to be split along an inclined plane 56 to define two hemispherical sections 58 and 60. The sections are held together by means of a plug 62 tapped at both ends to receive screws 64 and 66 and is formed with a diagonal opening 68 through its center portion which opening is slightly larger than the vertical passage 54 formed through the ball mount.

It will be understood that the two hemispherical sections 58 and 60 are held together by means of the plug 62 being tightened between the screws 64 and 66. In practice, the plug is inserted in position with the opening 68 lined up with the vertical passage and then the screw 66 is tightened so as to lock the plug in position. Next, the upper hemispherical section 60 is swiveled into the desired position so that the antenna will be generally predetermined relaupright. When the desired position is obtained, the screw 64 is tightened up to lock all of the components tightly together. With this arrangement, the antenna can be swiveled about the diagonal axis to any desired position and still maintain a passage through which the flexible nylon rod may extend.

The top portion of the hemispherical section will be seen to be tapped to accommodate a nipple to which is threaded a nut 72. The nipple carries an O ring 73 to form a seal between the nylon rod 34 and the nipple 70. The nut is secured tightly to the heavy coil spring 20 which has its upper end also connected to a nut 76. The function of the spring 20 is to provide resiliency for the antenna and to permit it to bend and flex under operating conditions. Extending through the center of the spring 20 and electrically connected to nuts 72 by soldering or the like, is a braided sleeve '78 of conductive material which serves to guide the nylon rod 34 through the center of the spring and also to complete the electrical antenna circuit between the nuts 72 and 76.

Threaded into the uppermost nut 76 is an annular nipple 88 which is screwed into a tubular base adapter 82. This adapter is formed with an internal annular shoulder 84 and receives the lower end of the tubular antenna section 18 in threaded engagement. The upper end of the section 18 is also threaded for engagement with a tapped annular locking cap 86 which is screwed over the top of the section 13. This cap is also formed with an interior annular shoulder 88 to bear against the upper end of the section 18. The cap is provided with an O ring 90 to provide a sliding seal for the neXt section 16 which slides through the cap into the section 18. A nylon bushing 92 is also provided. Extending radially through the cap is a tapped opening to accommodate a set screw 94, the inner end of which seats in a V groove 95 formed longitudinally along one side of the next upper section 16 to prevent the section 16 from being rotated from its assembled position for reasons that will presently appear.

Wound about the lower portion of the next tubular antenna section 16 is a light coil spring 96 of electrically conductive material, the lowermost end of which is soldered to a bushing 98 which is fixed to the lower end of the antenna section 16. This bushing is dimensioned to form a sliding fit with the inner walls of the lower antenna section 18. The upper end of the spring 96 will be seen to be formed with a hooked portion 100. This hooked portion hangs over the upper end of the section 18 and is clamped into position by means of the spring locking cap 86. The threaded upper end of the section 18 is formed with a notched recess to accommodate a downwardly extending leg 182 of the hooked portion 100 so that the cap may be readily threaded onto the upper end of the antenna section 18.

With this arrangement, the telescoped antenna sections are not only mechanically connected but also electrically connected through the spring 96. It will be understood that this positive electrical connection will be maintained no matter what the telescoped position the antenna is in and regardless of antenna movement such as whipping back and forth on an automobile or the like. That is to say, whether the antenna is fully extended, partially retracted or completely retracted, the several sections will be maintained in a positive electrical connection. When the antenna is telescoped into an extended position, the spring will be more or less compressed between the bushing 88 and the locking cap 86 as shown in FIG. 1. When the sections are retracted, the spring will be stretched as suggested in FIG. 2. When the antenna is extended and the spring compressed, no appreciable inductance is added to the antenna circuit since the adjacent convolutions of the spring will be pressed against one another.

It will be noted that the antenna sections 14 and 16 are connected by a similar arrangement employing a coil spring 184 and a spring locking cap 106 to form the positive electrical connection between the telescoping sections. As before, a longitudinal groove 107 is formed lengthwise of the section 14 to cooperate with a set screw 108 in the spring locking cap 106 to prevent rotation of the section 14 with respect to the section 16. By maintaining the several antenna sections in alignment with one another, there is no danger of the springs 184 and 96 becoming jammed which may be the case if either or both of the sections were turned so as to unwind or tighten up either or both of the springs.

The upper section 14 may be a solid piece tapped at its lower end to receive the threaded upper end of the flexible nylon rod 34 whereby, as the rod is advanced or retracted under the action of the motor, the several sections will telescope in and out. A cap 110 is threaded over the top of the section 14 to complete the assembly.

The antenna illustrated in FIGS. 1, 2 and 3 may be fabricated with any number of sections depending upon the length of the antenna desired. The length of the antenna will, of course, depend on the particular frequency being transmitted with the length typically being a quarter wavelength of the operating frequency. For some installations, however, the frequency being utilized may involve a wavelength which will require an antenna of such length as to be impractical to fabricate or mount. In such cases, the effective length of the antenna may be increased by center loading the antenna as suggested in FIG. 4. This involves the insertion of an electrically insulating tube 112 joining part of antenna sections 114 and 116. Wound about the tube 112 is a coil 118 the ends of which are electrically connected to the antenna section 114 and 116.

Tests on the present antenna have shown that the electrically conductive springs connecting adjacent telescopic sections provide improved antenna performance over a telescopic antenna without such connecting springs.

The test procedures involved mounting an antenna made according to the invention on a bench with no provision for ground plane elements and loading the antenna with a Heath GW 10 CB transmitter on 27.115 mes. A standing wave ratio bridge was connected in series with the transmission line and a field strength meter was placed two wavelengths from the antenna. The transmitter was 90% modulated with 400 cycle tone and the input to the final R.F. output tube was metered at 4.211 watts.

The test sequence was as follows: With a push-to-talk switch closed so as to place the antenna and transmitter in a transmitting mode the antenna length was adjusted for the lowest standing wave ratio; the field strength meter reading, which showed the relative power output, indicated 1.2 '(relative output/watts). The antenna was then moved from a vertical position of the antenna to a horizontal position and released for spring (mounting) action. The standing wave ratio varied from the vertical position of the antenna to the horizontal and from the horizontal to the vertical. The field strength readings were from 0 to 1.0.

The power to the antenna was shut off and all the antenna connections and mechanical joints were checked. No failures could be found.

With power again supplied to the antenna and the switch closed, the antenna was moved with a circular motion such as the antenna would undergo if mounted on a moving vehicle. The standing wave ratio did not vary and the field strength meter readings varied only with the proximity of the antenna to the field strength meter.

The antenna length was checked at 108 inches, the elements were disassembled and the above-mentioned springs were removed. The antenna elements were then reassembled without the springs and compression fittings were hand-tightened. The antenna length was readjusted to 108 inches.

With the antenna now without connecting springs, the push-t-o-talk switch was again closed and the standing wave ratio was noted as being higher with the field strength reading 1.0. The antenna was again moved with a circular motion and the standing wave ratio was again noted being higher. The field strength readings were from 0 to .75.

The antenna was moved from the vertical to the horizontal and under these conditions the standing wave ratio and field strength readings were too erratic to record.

It will be appreciated that the antenna illustrated and described herein is particularly useful in mobile transmitters since it provides an efiicient telescopic antenna in which a positive and permanent electrical connection is maintained throughout the entire length of the antenna under all operating conditions whether the antenna is extended, retracted or partially retracted and when the antenna is tilted or whipping back and forth.

While the invention has been described with particular reference to the illustrated embodiments, it will be understood that numerous modifications thereto will appear to those skilled in the art. Accordingly, the above description and accompanying drawings should be taken as illustrative of the invention and not in a limiting sense.

Having thus described the invention, what I claim and desire to obtain by Letters Patent of the United States is:

1. A telescopic radio antenna, comprising (a) a plurality of elongated conductive antenna sections telescopically connected to one another,

(b) an electrically conductive coil spring disposed between adjacent sections and about each inner telescoped section,

(c) one end of said spring being electrically connected to the telescoped inner end of one of said adjacent sections and the other end of said spring being electrically connected to the outer opposite end of the other of said adjacent sections to provide a positive uninterrupted antenna circuit between said adjacent sections through different telescoped positions.

2. A telescopic radio antenna according to claim .1 including an elongated member extending lengthwise through said sections and drivingly connected to at least one of said sections and power means for axially reciprocating said member to selectively extend or retract said sections.

3. A telescopic radio antenna according to claim 1 including guide means for maintaining said antenna sections in fixed rotational relationship and permitting sliding telescopic movement between adjacent sections.

4. A telescopic radio antenna comprising (a) a plurality of elongated conductive antenna sections telescopically connected to one another,

'(b) an electrically conductive coil spring concentrically disposed between adjacent sections,

(c) the upper end of said spring being electrically connected to the upper end of the outer adjacent sec tions and the lower end thereof being electrically connected to the lower end of the inner adjacent sections to provide a positive uninterrupted antenna circuit between said adjacent sections through differ. ent telescopic positions.

5. A telescopic radio antenna according to claim 4 including an annular antenna mount, said mount including two cooperating members normally connected along a plane inclined from the axis of said antenna, a stud extending through said members perpendicularly to said plane, screw means threaded to opposite ends of said stud for tightening said members together said stud being formed with a diagonal opening in register with the opening in said mount.

References Cited UNITED STATES PATENTS 2,498,350 2/ 1950 Walsh 343-900 XR 2,546,026 3/ 195-1 Coon 343O XR FOREIGN PATENTS 1,161,644 3/1958 France.

ELI LIEBERMAN, Primary Examiner. HERMAN KARL SAALBACH, Examiner. M. L. NUSSBAUM, Assistant Examiner. 

